In the era of ubiquitous computing, machine-to-machine (M2M) communication has attracted much attention. M2M communication technology is under study in many standard development organizations (SDOs) such as TIA, ATIS, ETSI, and oneM2M.
An M2M communication system may have a resource oriented architecture (RoA) and, thus, access to multiple resources may be efficient. Such access may be performed for the same operation (e.g., writing, reading, deleting, and execution) for the multiple resources.
If a group function is used in the RoA based M2M system, there is an advantage of simultaneously performing access to a plurality of group members. Through this group function, a group user may set a subscription capable of receiving a notification of information change of a group member. Next, the group user may aggregate notification messages of group members and transmit the aggregated messages as one notification message.
The group user may establish a notification policy for notification message transmission upon setting a subscription in a group. However, when the group user sets a plurality of subscriptions, it is difficult to factor in a policy per subscription.